Domodude17
Aluminum
- Joined
- Aug 14, 2017
Looking around, it seems like these lathes either came with a 1/4 or 1/2 hp motor. Would a 3/4 or 1 hp motor on a VFD be too much and damage something?
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What motor HP for 3 phase with VFD on 9"?
- Thread starter Domodude17
- Start date
- Replies 8
- Views 3,315
Dobermann
Hot Rolled
- Joined
- Jan 2, 2014
- Location
- North Carolina
1/2 HP is plenty for that lathe. I've been running mine with 1/3 HP and VFD for several years now and don't see any indication that it's underpowered. Unless you have the V-Belt drive option, it's going to be belt-slip limited by anything more than 1/2 HP. Higher power won't hurt anything but it's really wasted.
Domodude17
Aluminum
- Joined
- Aug 14, 2017
Thanks for the input guys. If I go with a 1/2 hp motor, is it worth it to get a VFD that's sized larger than that? Say a VFD sized for a 3/4 HP motor or a 1 HP motor?
500mpxlcameraguy
Aluminum
- Joined
- Feb 14, 2018
- Location
- Iowa USA
I’m running a 9A with a KBAC and a 1/2 HP and am very happy with the combination. I have not Been able to stall the motor, but I’m not too mean to it either. It’s a 9A after all.......
mandmj
Plastic
- Joined
- Mar 22, 2018
Mine has a 3/4hp DC motor w/ variable speed (a slightly different animal than the 3ph). I like the power, but I have stalled it a few times (using a serpentine belt, not leather). When that did happen, the blue chips were flying well! (carbide inserts of course).
steve-l
Titanium
- Joined
- Mar 2, 2012
- Location
- Geilenkirchen, Germany
All motors have an optimum speed where their efficiency is greatest. A VFD varies the speed of a 3 phase motor both above and below their most efficient speed. Even though a 1/2 HP motor is plenty for a SB 9, I would choose a 3/4 HP motor with a VFD for that reason. As an example of this practice, An older DoAll 16" band saw with a mechanical variable speed drive used a 1.5 HP motor. The same 16" DoAll band saw made today with a VFD uses a 3 HP motor for the same reason.
Domodude17
Aluminum
- Joined
- Aug 14, 2017
Just an update for anyone curious-I had picked up a VFD that is sized for up to 1-1/2hp simply because it wasn't more expensive and still had a small form factor. I still have the 1/2hp 3 phase motor on the lathe right now, but I found a guy selling a 3/4hp 3 phase motor for $5 (can't turn that down!) so i'm fixing that up and plan on installing it when it's finished up.
